4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
8 * This file contains the default values for the operation of the
9 * Linux VM subsystem. Fine-tuning documentation can be found in
10 * Documentation/sysctl/vm.txt.
12 * Swap aging added 23.2.95, Stephen Tweedie.
13 * Buffermem limits added 12.3.98, Rik van Riel.
17 #include <linux/sched.h>
18 #include <linux/kernel_stat.h>
19 #include <linux/swap.h>
20 #include <linux/mman.h>
21 #include <linux/pagemap.h>
22 #include <linux/pagevec.h>
23 #include <linux/init.h>
24 #include <linux/module.h>
25 #include <linux/mm_inline.h>
26 #include <linux/buffer_head.h> /* for try_to_release_page() */
27 #include <linux/percpu_counter.h>
28 #include <linux/percpu.h>
29 #include <linux/cpu.h>
30 #include <linux/notifier.h>
31 #include <linux/backing-dev.h>
32 #include <linux/memcontrol.h>
33 #include <linux/gfp.h>
37 /* How many pages do we try to swap or page in/out together? */
40 static DEFINE_PER_CPU(struct pagevec
[NR_LRU_LISTS
], lru_add_pvecs
);
41 static DEFINE_PER_CPU(struct pagevec
, lru_rotate_pvecs
);
44 * This path almost never happens for VM activity - pages are normally
45 * freed via pagevecs. But it gets used by networking.
47 static void __page_cache_release(struct page
*page
)
51 struct zone
*zone
= page_zone(page
);
53 spin_lock_irqsave(&zone
->lru_lock
, flags
);
54 VM_BUG_ON(!PageLRU(page
));
56 del_page_from_lru(zone
, page
);
57 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
61 static void __put_single_page(struct page
*page
)
63 __page_cache_release(page
);
64 free_hot_cold_page(page
, 0);
67 static void __put_compound_page(struct page
*page
)
69 compound_page_dtor
*dtor
;
71 __page_cache_release(page
);
72 dtor
= get_compound_page_dtor(page
);
76 static void put_compound_page(struct page
*page
)
78 if (unlikely(PageTail(page
))) {
79 /* __split_huge_page_refcount can run under us */
80 struct page
*page_head
= page
->first_page
;
83 * If PageTail is still set after smp_rmb() we can be sure
84 * that the page->first_page we read wasn't a dangling pointer.
85 * See __split_huge_page_refcount() smp_wmb().
87 if (likely(PageTail(page
) && get_page_unless_zero(page_head
))) {
90 * Verify that our page_head wasn't converted
91 * to a a regular page before we got a
94 if (unlikely(!PageHead(page_head
))) {
95 /* PageHead is cleared after PageTail */
97 VM_BUG_ON(PageTail(page
));
101 * Only run compound_lock on a valid PageHead,
102 * after having it pinned with
103 * get_page_unless_zero() above.
106 /* page_head wasn't a dangling pointer */
107 flags
= compound_lock_irqsave(page_head
);
108 if (unlikely(!PageTail(page
))) {
109 /* __split_huge_page_refcount run before us */
110 compound_unlock_irqrestore(page_head
, flags
);
111 VM_BUG_ON(PageHead(page_head
));
113 if (put_page_testzero(page_head
))
114 __put_single_page(page_head
);
116 if (put_page_testzero(page
))
117 __put_single_page(page
);
120 VM_BUG_ON(page_head
!= page
->first_page
);
122 * We can release the refcount taken by
123 * get_page_unless_zero now that
124 * split_huge_page_refcount is blocked on the
127 if (put_page_testzero(page_head
))
129 /* __split_huge_page_refcount will wait now */
130 VM_BUG_ON(atomic_read(&page
->_count
) <= 0);
131 atomic_dec(&page
->_count
);
132 VM_BUG_ON(atomic_read(&page_head
->_count
) <= 0);
133 compound_unlock_irqrestore(page_head
, flags
);
134 if (put_page_testzero(page_head
)) {
135 if (PageHead(page_head
))
136 __put_compound_page(page_head
);
138 __put_single_page(page_head
);
141 /* page_head is a dangling pointer */
142 VM_BUG_ON(PageTail(page
));
145 } else if (put_page_testzero(page
)) {
147 __put_compound_page(page
);
149 __put_single_page(page
);
153 void put_page(struct page
*page
)
155 if (unlikely(PageCompound(page
)))
156 put_compound_page(page
);
157 else if (put_page_testzero(page
))
158 __put_single_page(page
);
160 EXPORT_SYMBOL(put_page
);
163 * put_pages_list() - release a list of pages
164 * @pages: list of pages threaded on page->lru
166 * Release a list of pages which are strung together on page.lru. Currently
167 * used by read_cache_pages() and related error recovery code.
169 void put_pages_list(struct list_head
*pages
)
171 while (!list_empty(pages
)) {
174 victim
= list_entry(pages
->prev
, struct page
, lru
);
175 list_del(&victim
->lru
);
176 page_cache_release(victim
);
179 EXPORT_SYMBOL(put_pages_list
);
182 * pagevec_move_tail() must be called with IRQ disabled.
183 * Otherwise this may cause nasty races.
185 static void pagevec_move_tail(struct pagevec
*pvec
)
189 struct zone
*zone
= NULL
;
191 for (i
= 0; i
< pagevec_count(pvec
); i
++) {
192 struct page
*page
= pvec
->pages
[i
];
193 struct zone
*pagezone
= page_zone(page
);
195 if (pagezone
!= zone
) {
197 spin_unlock(&zone
->lru_lock
);
199 spin_lock(&zone
->lru_lock
);
201 if (PageLRU(page
) && !PageActive(page
) && !PageUnevictable(page
)) {
202 int lru
= page_lru_base_type(page
);
203 list_move_tail(&page
->lru
, &zone
->lru
[lru
].list
);
208 spin_unlock(&zone
->lru_lock
);
209 __count_vm_events(PGROTATED
, pgmoved
);
210 release_pages(pvec
->pages
, pvec
->nr
, pvec
->cold
);
211 pagevec_reinit(pvec
);
215 * Writeback is about to end against a page which has been marked for immediate
216 * reclaim. If it still appears to be reclaimable, move it to the tail of the
219 void rotate_reclaimable_page(struct page
*page
)
221 if (!PageLocked(page
) && !PageDirty(page
) && !PageActive(page
) &&
222 !PageUnevictable(page
) && PageLRU(page
)) {
223 struct pagevec
*pvec
;
226 page_cache_get(page
);
227 local_irq_save(flags
);
228 pvec
= &__get_cpu_var(lru_rotate_pvecs
);
229 if (!pagevec_add(pvec
, page
))
230 pagevec_move_tail(pvec
);
231 local_irq_restore(flags
);
235 static void update_page_reclaim_stat(struct zone
*zone
, struct page
*page
,
236 int file
, int rotated
)
238 struct zone_reclaim_stat
*reclaim_stat
= &zone
->reclaim_stat
;
239 struct zone_reclaim_stat
*memcg_reclaim_stat
;
241 memcg_reclaim_stat
= mem_cgroup_get_reclaim_stat_from_page(page
);
243 reclaim_stat
->recent_scanned
[file
]++;
245 reclaim_stat
->recent_rotated
[file
]++;
247 if (!memcg_reclaim_stat
)
250 memcg_reclaim_stat
->recent_scanned
[file
]++;
252 memcg_reclaim_stat
->recent_rotated
[file
]++;
256 * FIXME: speed this up?
258 void activate_page(struct page
*page
)
260 struct zone
*zone
= page_zone(page
);
262 spin_lock_irq(&zone
->lru_lock
);
263 if (PageLRU(page
) && !PageActive(page
) && !PageUnevictable(page
)) {
264 int file
= page_is_file_cache(page
);
265 int lru
= page_lru_base_type(page
);
266 del_page_from_lru_list(zone
, page
, lru
);
270 add_page_to_lru_list(zone
, page
, lru
);
271 __count_vm_event(PGACTIVATE
);
273 update_page_reclaim_stat(zone
, page
, file
, 1);
275 spin_unlock_irq(&zone
->lru_lock
);
279 * Mark a page as having seen activity.
281 * inactive,unreferenced -> inactive,referenced
282 * inactive,referenced -> active,unreferenced
283 * active,unreferenced -> active,referenced
285 void mark_page_accessed(struct page
*page
)
287 if (!PageActive(page
) && !PageUnevictable(page
) &&
288 PageReferenced(page
) && PageLRU(page
)) {
290 ClearPageReferenced(page
);
291 } else if (!PageReferenced(page
)) {
292 SetPageReferenced(page
);
296 EXPORT_SYMBOL(mark_page_accessed
);
298 void __lru_cache_add(struct page
*page
, enum lru_list lru
)
300 struct pagevec
*pvec
= &get_cpu_var(lru_add_pvecs
)[lru
];
302 page_cache_get(page
);
303 if (!pagevec_add(pvec
, page
))
304 ____pagevec_lru_add(pvec
, lru
);
305 put_cpu_var(lru_add_pvecs
);
307 EXPORT_SYMBOL(__lru_cache_add
);
310 * lru_cache_add_lru - add a page to a page list
311 * @page: the page to be added to the LRU.
312 * @lru: the LRU list to which the page is added.
314 void lru_cache_add_lru(struct page
*page
, enum lru_list lru
)
316 if (PageActive(page
)) {
317 VM_BUG_ON(PageUnevictable(page
));
318 ClearPageActive(page
);
319 } else if (PageUnevictable(page
)) {
320 VM_BUG_ON(PageActive(page
));
321 ClearPageUnevictable(page
);
324 VM_BUG_ON(PageLRU(page
) || PageActive(page
) || PageUnevictable(page
));
325 __lru_cache_add(page
, lru
);
329 * add_page_to_unevictable_list - add a page to the unevictable list
330 * @page: the page to be added to the unevictable list
332 * Add page directly to its zone's unevictable list. To avoid races with
333 * tasks that might be making the page evictable, through eg. munlock,
334 * munmap or exit, while it's not on the lru, we want to add the page
335 * while it's locked or otherwise "invisible" to other tasks. This is
336 * difficult to do when using the pagevec cache, so bypass that.
338 void add_page_to_unevictable_list(struct page
*page
)
340 struct zone
*zone
= page_zone(page
);
342 spin_lock_irq(&zone
->lru_lock
);
343 SetPageUnevictable(page
);
345 add_page_to_lru_list(zone
, page
, LRU_UNEVICTABLE
);
346 spin_unlock_irq(&zone
->lru_lock
);
350 * Drain pages out of the cpu's pagevecs.
351 * Either "cpu" is the current CPU, and preemption has already been
352 * disabled; or "cpu" is being hot-unplugged, and is already dead.
354 static void drain_cpu_pagevecs(int cpu
)
356 struct pagevec
*pvecs
= per_cpu(lru_add_pvecs
, cpu
);
357 struct pagevec
*pvec
;
361 pvec
= &pvecs
[lru
- LRU_BASE
];
362 if (pagevec_count(pvec
))
363 ____pagevec_lru_add(pvec
, lru
);
366 pvec
= &per_cpu(lru_rotate_pvecs
, cpu
);
367 if (pagevec_count(pvec
)) {
370 /* No harm done if a racing interrupt already did this */
371 local_irq_save(flags
);
372 pagevec_move_tail(pvec
);
373 local_irq_restore(flags
);
377 void lru_add_drain(void)
379 drain_cpu_pagevecs(get_cpu());
383 static void lru_add_drain_per_cpu(struct work_struct
*dummy
)
389 * Returns 0 for success
391 int lru_add_drain_all(void)
393 return schedule_on_each_cpu(lru_add_drain_per_cpu
);
397 * Batched page_cache_release(). Decrement the reference count on all the
398 * passed pages. If it fell to zero then remove the page from the LRU and
401 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
402 * for the remainder of the operation.
404 * The locking in this function is against shrink_inactive_list(): we recheck
405 * the page count inside the lock to see whether shrink_inactive_list()
406 * grabbed the page via the LRU. If it did, give up: shrink_inactive_list()
409 void release_pages(struct page
**pages
, int nr
, int cold
)
412 struct pagevec pages_to_free
;
413 struct zone
*zone
= NULL
;
414 unsigned long uninitialized_var(flags
);
416 pagevec_init(&pages_to_free
, cold
);
417 for (i
= 0; i
< nr
; i
++) {
418 struct page
*page
= pages
[i
];
420 if (unlikely(PageCompound(page
))) {
422 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
425 put_compound_page(page
);
429 if (!put_page_testzero(page
))
433 struct zone
*pagezone
= page_zone(page
);
435 if (pagezone
!= zone
) {
437 spin_unlock_irqrestore(&zone
->lru_lock
,
440 spin_lock_irqsave(&zone
->lru_lock
, flags
);
442 VM_BUG_ON(!PageLRU(page
));
443 __ClearPageLRU(page
);
444 del_page_from_lru(zone
, page
);
447 if (!pagevec_add(&pages_to_free
, page
)) {
449 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
452 __pagevec_free(&pages_to_free
);
453 pagevec_reinit(&pages_to_free
);
457 spin_unlock_irqrestore(&zone
->lru_lock
, flags
);
459 pagevec_free(&pages_to_free
);
461 EXPORT_SYMBOL(release_pages
);
464 * The pages which we're about to release may be in the deferred lru-addition
465 * queues. That would prevent them from really being freed right now. That's
466 * OK from a correctness point of view but is inefficient - those pages may be
467 * cache-warm and we want to give them back to the page allocator ASAP.
469 * So __pagevec_release() will drain those queues here. __pagevec_lru_add()
470 * and __pagevec_lru_add_active() call release_pages() directly to avoid
473 void __pagevec_release(struct pagevec
*pvec
)
476 release_pages(pvec
->pages
, pagevec_count(pvec
), pvec
->cold
);
477 pagevec_reinit(pvec
);
480 EXPORT_SYMBOL(__pagevec_release
);
483 * Add the passed pages to the LRU, then drop the caller's refcount
484 * on them. Reinitialises the caller's pagevec.
486 void ____pagevec_lru_add(struct pagevec
*pvec
, enum lru_list lru
)
489 struct zone
*zone
= NULL
;
491 VM_BUG_ON(is_unevictable_lru(lru
));
493 for (i
= 0; i
< pagevec_count(pvec
); i
++) {
494 struct page
*page
= pvec
->pages
[i
];
495 struct zone
*pagezone
= page_zone(page
);
499 if (pagezone
!= zone
) {
501 spin_unlock_irq(&zone
->lru_lock
);
503 spin_lock_irq(&zone
->lru_lock
);
505 VM_BUG_ON(PageActive(page
));
506 VM_BUG_ON(PageUnevictable(page
));
507 VM_BUG_ON(PageLRU(page
));
509 active
= is_active_lru(lru
);
510 file
= is_file_lru(lru
);
513 update_page_reclaim_stat(zone
, page
, file
, active
);
514 add_page_to_lru_list(zone
, page
, lru
);
517 spin_unlock_irq(&zone
->lru_lock
);
518 release_pages(pvec
->pages
, pvec
->nr
, pvec
->cold
);
519 pagevec_reinit(pvec
);
522 EXPORT_SYMBOL(____pagevec_lru_add
);
525 * Try to drop buffers from the pages in a pagevec
527 void pagevec_strip(struct pagevec
*pvec
)
531 for (i
= 0; i
< pagevec_count(pvec
); i
++) {
532 struct page
*page
= pvec
->pages
[i
];
534 if (page_has_private(page
) && trylock_page(page
)) {
535 if (page_has_private(page
))
536 try_to_release_page(page
, 0);
543 * pagevec_lookup - gang pagecache lookup
544 * @pvec: Where the resulting pages are placed
545 * @mapping: The address_space to search
546 * @start: The starting page index
547 * @nr_pages: The maximum number of pages
549 * pagevec_lookup() will search for and return a group of up to @nr_pages pages
550 * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
551 * reference against the pages in @pvec.
553 * The search returns a group of mapping-contiguous pages with ascending
554 * indexes. There may be holes in the indices due to not-present pages.
556 * pagevec_lookup() returns the number of pages which were found.
558 unsigned pagevec_lookup(struct pagevec
*pvec
, struct address_space
*mapping
,
559 pgoff_t start
, unsigned nr_pages
)
561 pvec
->nr
= find_get_pages(mapping
, start
, nr_pages
, pvec
->pages
);
562 return pagevec_count(pvec
);
565 EXPORT_SYMBOL(pagevec_lookup
);
567 unsigned pagevec_lookup_tag(struct pagevec
*pvec
, struct address_space
*mapping
,
568 pgoff_t
*index
, int tag
, unsigned nr_pages
)
570 pvec
->nr
= find_get_pages_tag(mapping
, index
, tag
,
571 nr_pages
, pvec
->pages
);
572 return pagevec_count(pvec
);
575 EXPORT_SYMBOL(pagevec_lookup_tag
);
578 * Perform any setup for the swap system
580 void __init
swap_setup(void)
582 unsigned long megs
= totalram_pages
>> (20 - PAGE_SHIFT
);
585 bdi_init(swapper_space
.backing_dev_info
);
588 /* Use a smaller cluster for small-memory machines */
594 * Right now other parts of the system means that we
595 * _really_ don't want to cluster much more
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